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Calcium intake and risk of fracture: systematic review

BMJ 2015; 351 doi: http://dx.doi.org/10.1136/bmj.h4580 (Published 29 September 2015) Cite this as: BMJ 2015;351:h4580
  1. Mark J Bolland, associate professor1,
  2. William Leung, health economist2,
  3. Vicky Tai, medical student1,
  4. Sonja Bastin, radiologist3,
  5. Greg D Gamble, biostatistician1,
  6. Andrew Grey, associate professor of medicine1,
  7. Ian R Reid, professor of medicine1
  1. 1Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
  2. 2Department of Public Health, University of Otago, PO Box 7343, Wellington 6242, New Zealand
  3. 3Department of Radiology, Starship Hospital, Private Bag 92024, Auckland 1142, New Zealand
  1. Correspondence to: M Bolland m.bolland{at}auckland.ac.nz
  • Accepted 18 August 2015

Abstract

Objective To examine the evidence underpinning recommendations to increase calcium intake through dietary sources or calcium supplements to prevent fractures.

Design Systematic review of randomised controlled trials and observational studies of calcium intake with fracture as an endpoint. Results from trials were pooled with random effects meta-analyses.

Data sources Ovid Medline, Embase, PubMed, and references from relevant systematic reviews. Initial searches undertaken in July 2013 and updated in September 2014.

Eligibility criteria for selecting studies Randomised controlled trials or cohort studies of dietary calcium, milk or dairy intake, or calcium supplements (with or without vitamin D) with fracture as an outcome and participants aged >50.

Results There were only two eligible randomised controlled trials of dietary sources of calcium (n=262), but 50 reports from 44 cohort studies of relations between dietary calcium (n=37), milk (n=14), or dairy intake (n=8) and fracture outcomes. For dietary calcium, most studies reported no association between calcium intake and fracture (14/22 for total, 17/21 for hip, 7/8 for vertebral, and 5/7 for forearm fracture). For milk (25/28) and dairy intake (11/13), most studies also reported no associations. In 26 randomised controlled trials, calcium supplements reduced the risk of total fracture (20 studies, n=58 573; relative risk 0.89, 95% confidence interval 0.81 to 0.96) and vertebral fracture (12 studies, n=48 967. 0.86, 0.74 to 1.00) but not hip (13 studies, n=56 648; 0.95, 0.76 to 1.18) or forearm fracture (eight studies, n=51 775; 0.96, 0.85 to 1.09). Funnel plot inspection and Egger’s regression suggested bias toward calcium supplements in the published data. In randomised controlled trials at lowest risk of bias (four studies, n=44 505), there was no effect on risk of fracture at any site. Results were similar for trials of calcium monotherapy and co-administered calcium and vitamin D. Only one trial in frail elderly women in residential care with low dietary calcium intake and vitamin D concentrations showed significant reductions in risk of fracture.

Conclusions Dietary calcium intake is not associated with risk of fracture, and there is no clinical trial evidence that increasing calcium intake from dietary sources prevents fractures. Evidence that calcium supplements prevent fractures is weak and inconsistent.

Footnotes

  • Contributors: MJB, WL, AG, and IRR designed the research. WL and MJB performed the literature search. WL, VT, SB, and MJB extracted or checked data. MJB and GDG performed the analyses. MJB drafted the paper. All authors critically reviewed and improved it. MJB is guarantor. All authors had access to all the data and take responsibility for the integrity of the data and the accuracy of the data analysis.

  • Funding: The study was funded by the Health Research Council (HRC) of New Zealand. MJB is the recipient of a Sir Charles Hercus Health Research Fellowship. The authors are independent of the HRC. The HRC had no role in study design, the collection, analysis, and interpretation of data, the writing of the article, or the decision to submit it for publication.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: the study was funded by the Health Research Council (HRC) of New Zealand. MJB is the recipient of a Sir Charles Hercus Health Research Fellowship; IRR has received research grants and/or honorariums from Merck, Amgen, Lilly, and Novartis; all other authors have no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: Not required.

  • Transparency statement: MB affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned have been explained

  • Data sharing: No additional data available.

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